Field of the Invention
The present invention relates to an apparatus for turning, unsettling and disturbing a large plurality of individual portions of food to promote the uniform and consistent application of a granular or powderized seasoning, an oil spray and/or other flavoring material that is dispensed in a food processing system. More specifically, the present invention relates to an improved tumble drum for use in the application of seasoning, oil and/or other flavoring material to individual portions of food.
Background of the Related Art
Tumble drums are used to apply a seasoning and/or an oil spray to foodstuffs consisting of a large plurality of individual food portions such as, for example, potato chips, popcorn or nuts. These and other foodstuffs of this type are suitable for the application of seasoning and/or oil spray by continuously turning, unsettling and disturbing the individual food portions placed within the drum by rotating the drum in a generally horizontal position or in a slightly downwardly canted position.
Tumble drums are generally moved by a machine and in a manner that causes the individual food portions to progressively move through the tumble drum from the inlet to the outlet. For example, a tumble drum may be canted slightly downwardly and off horizontal to cause food portions continuously deposited into the tumble drum at the inlet to progressively move through the tumble drum at a generally controlled rate until the individual food portions reach and then spill out of the outlet. During the time that an individual food portion remains within the tumble drum, which his referred to herein as the residence time, the tumble drum rotates to continuously disturb, turn and unsettle the individual food portions. This action ensures that all sides of each individual food portion receive seasoning and/or oil spray. It will be understood that the residence time is a function of, among other factors, the downwardly cant, i.e. the angle below horizontal, of the axis about which the tumble drum rotates. A larger downwardly cant will reduce the residence time and a smaller downwardly cant will increase residence time.
A tumble drum may be rotated about a horizontal axis of rotation instead of an axis of rotation having a downwardly cant. When a tumble drum is rotated about a horizontal axis, a means other than gravity must be provided to move the individual food portions through the tumble drum. In one embodiment, the tumble drum may be coupled to a differential impulse driver that reciprocates the tumble drum along the horizontal axis of rotation while the tumble drum is rotated. The reciprocation is characterized in that the rate of acceleration of the tumble drum is less in the direction of desired movement of the individual food portions than in the opposite direction. The greater rate of acceleration in the direction opposite to the desired direction of movement of the individual food portions causes the food portions to slide along the interior wall of the tumble drum more than the food portions will slide at the lower rate of acceleration in the desired direction of movement of the food portions. The result is that the individual food portions move within the tumble drum in the direction of the smaller rate of acceleration and opposite to the direction of the greater rate of acceleration. More details relating to differential impulse conveyance are included in U.S. Pat. Nos. 6,527,104 and 6,189,683 to Svejkovsky et al.
A downwardly cant of the axis of rotation of the tumble drum, or the stroke and/or rates of acceleration imparted by a differential impulse driver, may be optimized to achieve a desired residence time of the food portions within the tumble drum. The residence time of the food portion within the tumble drum and the rate at which seasoning and/or oil spray is deposited into the tumble drum will greatly influence the amount of seasoning and/or oil spray applied to each individual food portion during its time within the tumble drum. Flights may be provided on the interior wall of the tumble drum to prevent food portions from sliding circumferentially along the interior wall of the tumble drum as it rotates. The result is that the flights turn, disturb and unsettle the food portions along the interior wall as the drum rotates, but the flights are generally disposed axially along the interior wall of the tumble drum so as not to impair the movement of food portions from the inlet to the outlet.
A problem with conventional tumble drums is revealed when the rate of throughput of the food portions varies. The residence time of a given food portion, from the time it enters the inlet of the drum to the time that it exits the outlet of the drum, will be less at a low rate of throughput than at a higher rate of throughput. This is because the higher rate of throughput causes a greater amount of stacked food portions within each axial segment along the bottom “trough” of the tumble drum, and that greater load pushes against the food portions within the trough and ahead of the stacked food portions. The result is that the “stacking” of food portions within the tumble drum creates pressure that adds to the other forces that move food portions through the tumble drum and the food portions respond by moving through the tumble drum at a faster rate than would occur if the food portions moved at a rate determined solely by the downwardly cant of the tumble drum, or by the differential impulse driver, and not by the added application of force applied by the stacking of food portions within the trough of the tumble drum.
The rate at which seasoning and/or oil spray is applied to food portions moving through a tumble drum can be varied and is generally tailored to provide a uniform and consistent amount of seasoning and/or oil on each individual portion. This requires that the seasoning and/or oil dispensing apparatus operate at a rate that is based on the residence time of the individual food portions within the tumble drum where the seasonings and/or oil are applied. Any unwanted variation in residence time resulting from variations in throughput causes food portions to be seasoned and/or oiled inconsistently, with food portions with a longer residence time in the drum (due to lower throughput) receiving more seasoning and/or oil than food portions with a shorter residence time (due to higher throughput). It is advantageous to minimize the variation in residence time of food portions that move through a tumble drum.